Selective control and indication system



14, 1946. A. B. MILLER 2,490,257

SELECTIVE CONTROL AND INDICATION SYSTEM" Filed June 9, 1942' 3Sheets-Sheet; 1

A6 MK? A. B. MILLER SELECTIVE CONTROL AND INDICATION SYSTEM Filed June9, 1942 3 Sheets-Sheet 2 Patented May 14, 1946 UNITE ST TENT SELECTIVECONTROL AND INDICATION SYSTEM Alfred B. Miller, Edgewood, Pa., assignorto The Union Switch & Signal Company, Swissvale, Pa., a corporation ofPennsylvania Application June 9, 1942, Serial No. 446,399

1'? Claims.

My invention relates to selective control and indication systems, andmore particularly to systems for selectively controlling, indicating andtesting a plurality of electrical equipments.

Control and indication systems are frequently required to control aplurality of electrical equipments which are located at difierentlocations remote from the control point. In such systems it is desirablethat the condition of each of the difierent equipments be individuallyindicated at the control point to aid the operator. Also, it isdesirable that the operator be able to test from time to time thedifferent equipments to check their operative conditions withoutactually operating the equipment. Furthermore, it is in the interest ofsimplicity and economy that these functions be accomplished by use of asingle circuit extending between the control point and the locations ofthe different equipments.

A feature of my invention is the provision in systems of the class hereinvolved of apparatus incorporating novel and improved means forcontrolling, operating and testing from a central office a plurality ofremotely disposed electrical equipment and for indicating at such officethe condition of each such equipment, and wherewith these severalfunctions are accomplished by use of a single circuit between the ofiiceand the locations of the difierent equipments.

Another feature of my invention is the provision in systems of the typehere involved of apparatus incorporating novel mean wherewith theoperator can control and operate any one of a group of electricalequipments individually or control and operate the entire groupsimultaneously or control and operate selected ones of the groupsimultaneously.

Another feature of my invention is the provision of improved apparatusfor automatically indicating at a control point the occurrence of adesignated event at any one of a group of electrical equipments and toautomatically or semiautomatically operate the equipment at which suchevent occurs by energy supplied at the control point.

Another feature of my invention is the provision in systems of the typehere contemplated of improved apparatus wherewith a relatively largenumber of electrical equipments may be arranged in preselected groups,and the several groups controlled, operated and indicated by a singlecontrol means common to all of the differ ent groups.

An important feature of my invention is the provision of novel andimproved apparatus for automatically indicating at a central point whenand what mines of a submarine mine field are contacted by vessels andfor firing the contacted mines.

Another feature of my invention is the pro--;

vision of improved means for automatically firin-g themine on each sideof a contacted mine simultaneously with the firing of the contactedmine. I

Another feature of the invention is the provision of novel means forautomatically disarming all mines of a mine field that have for anyreason become armed.

Still another feature of the invention is the provision of novel meansfor manually firing any mine of a mine field whether or not such minehas been armed due to contact by a vessel.

Again, a feature of the invention is the provision of improved apparatusWherewith each mine of the mine field and the apparatus associatedtherewithcan be tested and indicated at the central control pointwithout firing the mine.

Other features, objects and advantages of my invention will appear asthe specification prograsses.

The above features, objects and advantages of my invention are attainedby using periodic currents of different preselected frequencies forselecting and indicating a plurality of electrical equipments, therebeing a different frequency for each equipment. I also use directcurrent of two different voltages, one voltage, a relatively lowvoltage, being used for the energization of control relays and similardevices, and the other voltage, a relatively high voltage, being usedfor operation of operating elements of the different equipments. I usein addition alternating current of a relatively low voltage andpreselected frequency as a current of a particular characteristic forresetting and testing the equipments and, under certain circumstances,for conditioning a selected equipment for subsequent operation. Theseseveral sources of current are located at the control oflice and currentfrom each source is supplied to the equipments through a transmittingcircuit. Because of the different characteristics of the differentcurrents, a single two-conductor transmitting circuit can be used, thiscircuit extending from the oflice to a distribution point or stationlocated convenient to the electrical equipments and from whichdistribution point or station current is delivered to the equipmentsover multiple extensions of the transmitting circuit. Frequencyresponsive receiving devices or relays, one for each electricalequipment, are provided at the distribution point and connected to thetransmitting circuit in multiple, each device being energized only byperiodic current of the frequency preselected for the respectiveequipment. Each such receiving device when energized functions to extendthe transmitting circuit to the respective equipment so that control,operation and testing currents supplied'to the transmitting circuitsubsequent to such selection are delivered to the selected manually asdesired.

Automatic operation of the control means is effected in response to theoccurrence of a prede-i termined event at any one of the equipments bythe transmitting circuit being normally excited by the low voltagedirect current source and a normally open contact, one at each of suchequipments, being closed to complete a low resistance shunt path acrossthe transmitting circuit when the predetermined eventoccurs at theequipment. Such low resistance shunt path across the transmittingcircuit causes an impulse of current to flow in the transmitting circuitand an ofiice means connected to the circuit is energized thereby toinitiate an operation of thecontrol means. Operation of one series ofthe successively operated contacts of the control means connects thesources of periodic current one at a time to the transmitting circuitfor selectively exciting the receiving devices and then subsequentlyconnecting the source of operating current or the source of current ofparticular characteristic for operating the respective equipment or fortesting and resetting of such equipment as predetermined by the operatorat the oifice. The operation of this serie of contacts or a similarseries of contacts successively connects indication devices one at atime to the transmitting circuit to indicate the selected equipment,

there being a particular indication device for each electricalequipment. Manual operation is effected through manually operablecircuit controllers provided at the office and by which the operator cangovern the control means and the connections of the several currentsources to the transmitting circuit.

Where a relatively large number of electrical equipments are required, Iprefer to arrange them in groups with each group provided with adistribution point which has its own transmitting circuit from theofiice. The office control means is then provided with additional seriesof successively operated contacts, so that the oflice current sourcesand indication devices are conneoted to the different transmittingcircuits.

I shall describe one form of apparatus embodying my invention and shallthen point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1a, lb and when arranged in theorder named, with Fig. 1a placed at the left, are a diagrammatic viewshowing one form of apparatus embodying my invention when used for amine field. It is to be understood that I do not limit my invention tomine fields, and this one illustration is merely an example of manyapplications for my invention.

Referring to the drawings, the reference character OF (Figs. 1a and 1b)designates an office, with which is associated a mine field comprising anumber of mines (Fig. 10) each designated by the reference character Mwith a distinguishing suflix. The office OF may be on shore in thevicinity of a harbor that is to be defended by the mine field. Only sixmine MI" to M5, inelusive, of the mine field are shown since these aresufficient to fully illustrate the invention. It is contemplated thatthe mine field would consist of a relatively large. number of mines, and

mines MI, M2 and M3 are three mines of a first or station DH, and minesM4, M5 and M6 are three mines of a second group of mines common to adistribution point DP2. It is to be understood, of course, that eachgroup of mines may include additional mines and that the mine field mayinclude additional groups.

The distribution points DPI and DP2 may be in suitable housings anchoredat convenient points in the harbor.

A transmitting circuit extends between the officeOF and each of thedistribution points DPI and DP2, the circuit to distribution point DPIincluding a. single conductor cable Ll as one side of the circuit, andthe circuit to distribution point DP2 including a single conductor cableL2 as one side of that circuit. The return side of each transmittingcircuit is completed through the ground although a metallic conductorcan be used. Each such transmitting circuit is extended from therespective distribution point to each mine of the associated group ofmines by a circuit extension including a single conductor cable andground, cables S I, S2 and S3, extending from distribution point DPI tomines MI, M2 and M3, respectively, and single conductor cables S4, S5and S6, extending from distribution point DP2 to mines M4, M5 and MB,respectively. That is to say, each transmitting circuit is atwo-conductor circuit which as disclosed includes a single conductorcable as one side of the circuit and the ground path as the other sideof the circuit.

The oflice equipment is disclosed in Figs. 1a and 1b, and comprises asessential elements sources of periodic current of different frequencies,two sources of direct current, a source of current of a particularcharacteristic, control means, indi cation means and manually operablecircuit controlling devices. The sources of periodic current compriseoscillators OSI, OS2 and 083, and which oscillators are shownconventionally since they may be of any One of several well-known typesof construction, such as electron tube oscillators. It is suflicient forthis disclosure to point out that oscillators O31, OS2 and 033 areconstantly active to deliver periodic currents of different fre--quencies, which I shall designate as frequency fl, f2 and f3,respectively. In practicing the invention there would be provided adifierent oscillator for each mine of each group of mines, so that thereWould be a different frequency for each mine of each group. In thepresent disclosure. oscillator 05! which supplies currentof thefrequency fl, is associated with the first mine-Ml of. the first groupof mines, and also with the first mine M4 of the second group of mines.Oscillator 0S2 which supplies current of the frequency f2, is associatedwith the second mine M2 of the first group, and with the second mine M5of thesec- 0nd group, and in like manner oscillator 083 which suppliescurrent of the frequency f3, is associated with mines M3 and MB of therespec tive groups of mines.

Batteries BI and B2 are the two office sources of direct current,battery Bl supplying current at a relatively low voltage, such as, forexample 30 volts, and battery B2 supplying current of a relatively highvoltage, such as, for example, 600 volts. The battery Bl which supplies30 volts is used for control and indication purposes, while th batteryB2 which supplies 600 volts, is used for operation purposes. The sourceof current of particular characteristic is a transformer Tl, primarywinding 20 of which is connected to any convenient source of 60 cyclealternating current, having terminals indicated at BX and CX. That istosay, the current of' particular characteristic here employed is a 60cycle alternating current. It is to be understood that the invention isnot limited to the above frequencies, voltages and characteristics ofthe difierent currents, and that other frequencies, voltages andcharacteristics may be used if desired.

The office control means comprises a group of chain or stepping relaysll, 1, 2, 3 and 6; transmitting relays T, X, Y, El and Z2; and deliveryrelays CO, RS, PP and LK, these difierent relays of the control meansbeing operated in a stepby-step manner through a predetermined operationcycle. As will appear hereinafter, the stepping relays l, 2 and 3 areprovided with contacts which are arranged in different series. Oneseries of contacts connects the oscillators one at a time to thetransmitting circuit extending to distribution point DPl. As disclosed,this same series of contacts connects different sets of indicationrelays one set at a time to this transmitting circuit, although adiiferent series of contacts for the indication relays may be used.Similarly, another series of contacts connect the oscillators and otherindication relays to the transmitting circuit extending to distributionpoint DP2. Additional relays K, Kl, K2, W, WI, WP, I, BG, CR and I2 areassociated with the control means for initiating, arresting andterminating the operation cycle of the control means.

The ofiice indication means comprises a group of indication relays foreach mine group, there being a main indication relay MK, plusadistinguishing numeral, and an auxiliary indication relay A, plus adistinguishing numeral, for each mine. For example, main indicationrelay MKI and auxiliary indication relay A! are associated with mine Ml.

Th manually operable devices at the office are two-position circuitcontrollers each designated by the reference character P with adistinguishing prefix, and which controllers may be spring return typeof push button or may be non-biased switches.

Each distribution point DPl and DPZ is provided with a frequencyresponsive receiving device or relay for each mine associated with suchdistribution point, receiving devices Rl, R2 and R3.

being provided at distribution point DPI for mines Ml, M2 and M3,respectively; and receiving devices R4, R5 and R6 being shown at dis-,tribution point DP2 for mines M4, M5 and M6, respectively. Thesereceiving devices are preferably similar in construction and may be ofany one of several forms of frequency responsive relays. As heredisclosed, receiving device RI, for example, comprises a filter MFI anda cold cathode gas triode electron tube 2 l. Filter MFI connects tube 2|to the transmitting circuit, the input side of filter MFl beingconnected between conductor LI and ground electrode 22, and its outputside being connected between cathode 33 and a control electrode 3 3 ofthe tube 2 l. Filter MFl is proportioned to pass current only of thefrequency fl, that is, to pass only current supplied by oscillator 0S!at the ofiice, and which oscillator is the one associated with the samemine Ml with which receiver Rl is associated. Thus when periodic currentof the frequency Fl is supplied to the transmitting circuit extending todistribution point DPl, an electromotive force is applied acrosselectrodes 34 and 33 of tub 2|,

and the tube is excited and conditioned to become ionized if at the sametime a proper volta e is applied to the anode 35 of the tube. The partsare'so proportioned that tube 2l is ionizedand becomes conductive when avoltage from battery Bl or B2 or transformer Tl is applied to the anodeof the tube at a time the control electrode 34 is excited through filterMFI. The remaining receiving devices are of like construction except forthe tuning of the respective filter. Filter MFZ of receiving device R2is proportioned to pass only current of the frequency f2, that is, onlythat supplied by oscillator 0S2, which is the oscillator associated withmine M2 with which receiving device RZ-is also associated. Atdistribution point DPZ, a filter MW of the receiving device R4 isproportioned to pass only current of the frequency fl, the same filterMFI of the receiving device RI, and filter MF5 is proportioned to passonly current of the frequency of i2, the same as filter MF2. It followsthat when periodic current of the frequency of is supplied to thetwotransmitting circuits, the receiving devices RI and R4 are excited andbecome conditioned to be ionized if a voltage from battery Bl or B2 ortransformer Tl is supplied to the transmitting circuits at the sametime. Likewise, receiving devices R2 and R5 are excitedand becomeconductive if oscillator CS2 is connected to the transmitting circuitsalong with either battery Bl or B2 or transformer T-l. The receivingdevices R3 and R6 are shown conventionally only for the sake ofsimplicity, since their construction is similar to that of the otherreceiving devices except for the fact that the filters of receivingdevices R3 and R6 are tuned to pass only current of the frequency of f3which is the frequency for oscillator 0S3 associated with mines M3 andMS with which receiving devices R3 and R6 are also associated. Themanner whereby each receiving device when rendered conductive extendsthe transmitting circuit to the respective mine will be explained later.Each distribution point is also provided with two relays designated LLand LP with appropriate numerals, and the functions of these relays willalso appear later.

The electrical equipment at each mine comprises an operating element inthe form of a detonator, a circuit controller in the form of an armingswitch, a filter and a relay, these devices being identified by thereference characters D, AS, FT and MR,respectively, plus a numeralcorresponding to the numeral of the mine. These mine equipments are allalike, and a description of one will suffice for all.

Referring to mine Ml, for example, its filter FTI has its input sideconnected between cable SI and ground electrode 36, and its output sideconnected to relay MRI through a full wave rectifier 25 as will beapparent by an inspection of Fig. 10. Filter FTI is proportioned to passonly current corresponding to the frequency of the particularcharacteristic current, that is, to pass only current corresponding to60 cycle alternating current, and hence when current of 60 cycles ispassed by the receiving device Rl to the circuit extension includingcable SI, the relay MRl is energized by unidirectional current.Detonator D! is of the usual form and is active to fire the mine whencurrent of 600 volts is supplied thereto, but current of 30 volts assupplied by battery Bl or current of a volta e supplied by transformerTI is insufficient to actuate the detonator. Arming switch ASl maybean'y one of several known types, and as here disclosed it includes atilting member 26 which is mounted on the mine to normally occupy ahorizontal position, that is,

the position shown in Fig. 1c, and to be tilted about apivot 21 when avessel contacts themine.

At the normal position of the switch, the member 26 engages a contactmember 28 to hold contact member'28 to the left in opposition to a biasspring 29, but when a vessel contacts the mine and member 26 is tiltedto swing free of contact member 28, contact member 28 is moved to theright under the force of spring 29 to engage a contact 30' and arm themine by completing a circuit path from ,detonator D1 to ground electrode32. Contact 30 is attached to armature 3| of relay MR1. When relay MRIis energized to attract its armature 3!, with the arming switch ASI inits normal position, the contact 36 is moved to engage contact member 28and arm the mine. If arming switch AS! has been previously actuated toarm the mine, and the mine has not been fired, then energization ofrelay MRI to attract its armature 3| forces contact member 28 to theleft in opposition to spring 29, and resets the arming switch ASI sothat subsequent deenergization of relay MRI disarms the mine. Theconstruction of the equipment for each of the other mines is the same asthat described for mine MI, the equipments for mines M2, M4 and M5 beingshown complete, but those for mines M3 and M6 being shown conventionallyonly in order to simplify the drawings as much as possible. I

It should be pointed out at this time that three different types ofdirect current relays, neutral, stick polar and biased polar areemployed. The neutral relays operate to close front contacts whencurrent of either polarity is applied to its winding and to close backcontacts when the relay is deenergized. The stick polar relays aretwowinding relays and are characterized by the fact that when the relayis deenergized the polar armature of the relay remains in the positionto which it was last moved. 'In the drawings each stick polar relay isoperated to close normal or left-hand contacts as viewed in the drawingsonly when positiveenergy is applied to the left-hand side of a windingof the relay, and is operated to close reverse or right-hand contactsonly when positive energy is applied to the right-hand side of a windingof the relay. The biased polar relays are either one or two-windingrelays, and the armature of each relay is biased, by means hereillustrated as a spring, to the reverse or righthand position. Eachbiased polar relay is operated to close normal or left-hand contactsonly when positive energy is applied to the left-hand side of a windingof the relay. Positive energy applied to the right-hand side ofa windingof a biased polar relay aids the bias to hold the relay at its reverseposition. The normal and reverse contacts of each polar relay aredesignated N and R, respectively, with a proper numeral. Many of therelays are provided with a predetermined slow release period by anasymmetric unit connected in the usual well-known manner across awinding of the relay. In some instances, to avoid complexity in thewiring diagram, relay contacts are shown remote from the winding of therelays.

which control those contacts, and in each such instance the relaycontact is identified by a ref erence character corresponding to that ofthe associated relay.

The apparatus of the system can be conditioned for either full automaticoperation, or for semiautomatic operation, or for manual operation, and.in describing the operation of the apparatus I shall consider thesethree different conditions in the order named. In describing each suchcondition, a brief outline of the operation of the apparatus under thatcondition will be first given, and then the operation of the apparatuswill be set forth in a step-by-step manner.

-W-hen the system is set for full automatic operation the apparatus isnormally in an alert condition and the contacting or arming of a mine ormines initiates an operation cycle of the equipment at the ofiflce thatfirst indicates what mines have been armed, fires all the armed mines,and then disarms all the mines that may have become armed due to theshock of firing the adjacent mines. The apparatus then assumes thenormal or alert condition and remains thus until another mine iscontacted. At this time, another operation cycle, identical to the oneabove will be initiated, and the contacted mine or mines will beindicated and fired and the other mines disarmed. This indicating,firing and disarming will be repeated automaticall each time an unfiredmine in the field is armed by engagement with a vessel. Manual operationof a push button or switch when the system is set for automaticoperation will cause one mine on each side of a contacted mine to beautomatically fired when the contacted mine is fired.

In the drawings the apparatus is shown in the normal or alert conditionfor automatic operation and under such alert condition, the ofiiceoscillators OSI, CS2 and CS3 are active, and the neutral relays W and'Wland stick polar relays Z! and Z2 are energized. Relays W, ZI and Z2 areenergized in series by current supplied from positive terminal B ofbattery Bl through a normally closed contact 31 of a manually operableswitch 2P, reverse contact IR of stick polar relay K, winding of relayW, and the lower windings in series of relays Z2 and Z! to negativeterminal C of battery BI. Thus relay W is picked up and relays Z l andZ2 are operated to th right. Relay WI is energized over an obviouscircuit including reverse polar contact 2R of relay K.

At distribution point DPI biased polar relay LL! and neutral relay LPIare normally energized by current supplied to the transmitting circuitby the control battery Bl, current flowing from positive terminal B ofbattery Bl through reverse polar contact 3R of relay K, ground elec-,

trode 39 and ground path to ground electrode 40 at distribution point DPtop winding of relay LLI, asymmetric unit 4 I impedance 42, conductor Llback to the ofiice OF, front contact 43 of relay Wl, winding 44 of atransformer T2 to be referred to later, and reverse polar contact 4B. ofrelay K to terminal 0 of battery Bl. Relay LLl is operated to the leftand closes at its IN contact a circuit path by which current flowsthrough the lowerwindin-g of relay LL! and winding of relay LPi inmultiple with the top winding of relay LLI so that relay LPI as Well asrelay IL! is energized. Relay LPI on picking up closes front contacts45, 46 and 4'6 to connect conductor Ll to each of the conductors S l S2and S3 extending to the mines Ml, M2 and M3, respectively, Fuses 48, 49and l2lare interposed in conductors SI, S2 and'S3, respectively.Similarly, relays LLZ and LP2 at distribution point DP2 are normallyenergized by current'supplied from battery Bl to the transmittingcircuit extending to distribution point DP2, current flowing fromterminal B through the 3R contact of relay K to ground andthe groundpath to ground electrode 50' at distribution point DP2, and thencethrough top winding of relay LL2, asymmetric unit 5|, vimformer T3 to bereferred to later, and 4R contact of relay K to terminal C. Relay LL2 isoperated to close its normal contact IN and current flows through thelower winding of relay LL2 and the winding of relay LPZ in multiple withthe top winding of relay LLZ, so that relay LP2 is energized and pickedup closing front contacts 55, 56'and I28 to connect conductor L2 to theconductors S4, S and S5 extending to mines M4, M5 and M6, respectively.At distribution point DP2 fuses 5T, 58 and I29 are interposed in theconductors S4, S5 and S6, respectively. It follows that eachtransmitting circuit is normally excited and each mine of each group ofmines is normally in circuit with the respective transmitting circuit.

I shall assume that mines MI and M5 are contacted by vessels to actuatethe respective arming switches ASI and A85 to arm these mines in themanner explained hereinbefore. The closing of contact 283Ii of switchASI completes a low resistance shunt path from conductor LI to groundthrough front contact of relay 'LPI, fuse 48, conductor SI, impedance83, detonator DI and contact 283!l to groundelectrode 32. This lowresistance shunt path shunts relays LLI and LPI, and relay LLI isoperated to its biased position and relay LPI is released. The releaseof relay LPI to open front contacts 45, 4'5 and 4'! opens the normalconnections of conductors SI, 0

S2 and S3 to conductor LI so that thereafter the conductors SI, S2 andS3 can be connected to conductor LI only through the respectivereceiving devices RI, R2 or R3, as will be shortly explained. Similarlythe relays LLZ and LPZ at distribution point DP2 are shunted due to thelow resistance path completed through contact 59-60 of arming switchAS5, and conductors S4, S5 and S6 are disconnected from conductor L2, sothat thereafter these conductors S4, S5 and S6 can be connected toconductor L2 only through the respective receiving devices R4, R5 or R5.

The momentary increase in the flow of direct current in conductor LI,due to the shunt path completed at the arming switch ASI induces anelectromotive force in winding 6! of transformer T2 at the office, andbiased'polar relay KI connected to winding BI is momentarily energizedat a polarity that operates it to its normal position. In like manner,biased polar relay K2 is operated momentarily to close its normalcontact IN by the electromotive force induced in transformer T3, due tothe increase of current flowing in conductor L2 caused by the closing ofthe shunt path through the arming switch ASE. With either relay KI or K2operated to close its normal contact IN, current flOWs from terminal Bthrough the top winding of relay K, front contact I9 of relay W, andback contact 62 of relay WP to terminal C, and relay K is operated toits normal position, and being a polar stick relay, it remains in itsnormal position subsequent to the dying away of electromotive forcesthat momentarily operated relays KI and K2. It is obvious thatthecontacting of any mine in any group of mines, re-

gardless of the number of mines in a group or the number of groups inthe mine field, will cause relay K at the office to be operated to itsnormal position.

This operation of relay K to its normal position initiates an operationcycle of the office I control means that first indicates what mines havebeen contacted, then fires the contacted mines and then disarms allmines that become armed due to the shock of firing the contacted mines.At the first step of the operation cycle,

the circuits for relays W and WI are opened at the respective IR and 2Rcontacts of relay K, and relay WI releases at once and relay W releasesat the end of a predetermined slow release period. Relay WI uponreleasing to open front contacts 43 and 53, opens the normal connectionsof battery BI through transformers TI and T3 to the respectivetransmitting circuits, so that no further operation of relays KI and K2can take place during the operation cycle. During the slow releaseperiod of relay W current flows from terminal B through normally closedcontact 31 of switch 2?, IN contact of relay K, front contact 63 ofrelay W, the two windings in series of biased polar relay X, backcontact 64 of relay T, reverse polar contact 2R of relay'ZI, and thelower winding of stick polar relay Y to terminal C. This operates relayX to close its normal contacts and relay Y to close its normal contactsif relay Y is not already in its normal position. Relay X thus operatedto the left provides for itself a stick circuit at its contact IN sothat relay X is held to its normal position after relay W releases toopen front contact 63. After relay X is operated, and before relay W isreleased, current is supplied to neutral relay ll of the stepping relaysin series with stick polar relay CR, current passing from terminal Bthrough contact 2N of relay K, contact 2N of relay X, contact SE. ofrelay ZI, front contact 65 of relay W, wire use, winding of relay I andtop winding of relay CR to terminal C. Relay 0 is picked. up andprovides through Wire IBI and its front contact 66 a stick circuit bywhich it is retained energized after relay W is released. Relay CR isoperated to its normal position, and being a stick polar relay itremains in its normal position until the indication portion of theoperation cycle is finished, as will later appear. When relay K isoperated to its normal position, the connection of battery BI isreversed at contacts 3N and. 4N of relay K so-that the LL and LP relaysat the different distribution points cannot be again energized duringthe operation cycle, current, being blocked by the asymmetric units 4|and SI of the distribution points.

At the next step of the operation cycle, relay W is released. Release ofrelay W to close back contact energizes neutral relay WP over an obviouscircuit, but relay WP performs no useful function at this time. Neutralrelay I also receives current from terminal B through back contact 61 ofrelay W, Wire I62, 3N contact of relay CR, front contact 68 of relay El,wire I63, winding of relay I and contact 69 of a push button 3P toterminal C. Relay I picks up and provides a stick circuit for itselfthrough its own front contact Ill and wirelfifl, and remains energizeduntil relay GR is reversed at the end of the indication portion of theoperation cycle. Relay I on picking up to close front contacts 82, 91,I0, I01, I23 and I38 prepares circuits for the different sets ofindication relays, andwhich circuits are closed one at a time by thestepping relays as the operation cycle progresses. Neutral relay T isalso energized by a circuit extending fromterminal B through backcontact II of relay W, 3N contact of relay Y, wire I65, front contact I2of relay 0, wire I66 and winding of relay T to terminal C. The pickingup of relay T to open back contact 6t and close front contact '13 shiftsthe circuit through relay X from the lower winding of relay Y to the topwindings in series of relays Z! and Z2, since contact IN of relay Y isclosed. This causes relays ZI and Z2 tobe operated to their hornalpositions with relay Y" remaining at its normal position-because itis of the stick polar type, Relay X is slow acting and is not operateclby its bias during the interval the contacts of relay T1 are in transit.

Relay ZI when op'eratedto its normal position, starts the next step ofthe operation cycle. Stepping relay I1 is deenergized by the opening ofthe 3R contact of relay ZI and relay I] releases at the end of -apredetermined slow release period. The next relay I of the steppingrelays receives energy during the slow release period of relay 0,current fiowingfrom terminal B through 2N contact of relay K, 2Ncontactof relay X, 4N contact'of relay ZI, wire I61, front contact I4'of relay 8,!and winding of relay I to terminal C. Relay on picking upprovides a stick circuit for itself at its own front contact I5. Withrelay released and relay I picked up current is supplied to relay CO,current flowing from terminal B through IN contact of relay Z2, wireI68, back contact I6 of relay 0,,front contact 1'! of relay I andwinding of relay CO to terminal C. With relays I and CO picked up, theoscillator OSI and the battery BI in series with indication relays ofthe first mine of each group, are connected to the transmittingcircuits. At distribution point DPI the filter MP! is the only one tunedto pass cur rent of the II frequency, and hence periodic current flowsfrom oscillator OSI through wire'18, condenserr'w, front contacts 80 andSI of relays I and CO, respectively, conductor LI, filter MFI and groundbetween electrodes 22 and 39 to oscillator OSI ,The current thus passedby filter MFI excites tube 2| of receiving device RI. Since mineMI isassumed to be armed, a direct voltage from battery BI is now applied toanode of tube 2| simultaneously with the exciting of thecontrolelectrode 34 of the tube by the periodic current from oscillatorOSI, the circuit from batteryBI being traced from terminal B through 3Ncontact ofrelay K, winding of biased polar indication relay AI, topwinding of stick polar indication relay MKI, front contact 82 of relayI, wire I69, front contacts 80 and 8| of relays I and CO, respectively,conductor LI, anode 35 and tube space tocathode 33 of tube 2I, fuse 48,conductor SI, impedance 83, detonator DI, contact 28-30 of switch ASI,ground path between electrodes 32 and 39, and 4N contact of relay K toterminal C. Tube 2I breaks down and direct current flows, the currentbeing of suflicient value to operate indication relays AI and MKI butinsufficient to fire detonator DI. Relay MKI is operated to the left toclose its IN contact to complete an obvious circuit for an indicationlamp LM I, and that lamp is illuminated to indicate the armed conditionof mine MI. Relay MKI being of the stick polar type, it remains at itsnormal position until the indications are cancelled at the end of theopera-' tion cycle. Relay MKI also prepares a circuit to be shortlydescribed, for automatically firing mine MI. The function of relay AIwill be explained hereinafter. action at distribution point, DPI,periodic current from oscillator OSI is supplied to distribution pointDPZ, the connection of oscillator, OSI to conductor L2 of thetransmitting circuit extend- Simultaneously with this However, mine M4is not at this time armed and the'circuit from battery BI to the anodeof tube 86'is open at arming switch A84, with the result that the tubeis not broken down, and no indication current flows to operateindication relays A4 and MK4 associated with mine M4, relays A4 and MK4being interposed in a circuit connection from battery BI 'to conductorL2 through front contact IIl'I of relay I, wire I13 and front contacts84 and 85. of relays I and CO. It is obvious from the above that thearming of the first mine of each group of mines will be simultaneouslyindicated in the manner by which mine MI is indicated during this stepof the operation cycle.

Release of relay 0 at the beginning of this step of the operation cyclecauses operation of relays T, Y, ZI and Z2. Release of relay I) to openfront contact 12 deenergizes relay T, and relay T is at once released.The release of relay T to open front contact I3 and close back contact64 shifts the circuit through relay X from the top windings of relays ZIand Z2 to the top winding of relay Y, the connection including INcontact of relay ZI. The relay Y is operated to the right to its reverseposition, and relay T is reenergized and picked up bythe circuitcompleted at back contact II of relay W, 3R contact of relay Y, wireIII, front contact 81 of relay I and wire I66.

The picking up of relay T to open back contactv 64 and close frontcontact I3 shifts the circuit through relay X from the top winding ofrelay Y to the lower windings of relays ZI and Z2, because contact IR ofrelay Y is now closed.

Relays ZI and Z2 are now operated to the right to close their reversecontacts, to start the next step of the operation cycle. When relay Z2is operated to the right, opening its IN contact, the relay CO isdeenergized and immediately releases to open the connections by'whichoscillator OSI and battery BI are connected to the transmitting circuitsand all energy to the tubes of the respective receiving devices and tothe respective indication relay is withdrawn. When relay ZI operates tothe right opening its 4N contact and closing its 3R contact, relay I isdeenergized and releases at the end of its slow release period and thenext relay 2 of the stepping relays is picked up by current suppliedfrom contact 88 of relay 5 and Winding of relay 2 to' 7 terminal C.Relay 2'on picking up provides a stick circuit for itself at its ownfront contact 89. When relay I releases opening front contacts and 84,the respective indication relays for the first mine of each group arefurther disconnected from the transmitting circuits and remaindisconnected for the remaining portion of the operation cycle. mains atits normal position to continue the illumination of the indication lampLMI. With relay I released and relay 2 picked up, the CO relay isrcenergized over a circuit including terminal B, the 2R contact of relayZ2, Wire I72,

back contact'9l of, relay I, front contact 92 of relay 2, winding ofrelay CO and terminal C. With relays 2 and CO picked up, oscillator CS2and the indication relays for the second mine of'each group in serieswith battery BI are connected to the transmitting circuits. Theconnection of oscillator CS2 to conductor Ll of the first transmittingcircuit includes wire 93, con: denser 94 and front contacts 95 and 8I ofrelays 2 and' CO, respectively; and the connection to conductor L2 ofthe second circuit includes However, relay MKI rewire 93, condenser I83,front contact 98 of relay 2 and front contact 85 of relay CO. Filter MP2is the only one at distribution point DPI tuned to pass current of thefrequency 12 and the tube 96 of receiving device R2 is excited, butsince mine M2 is not armed the extension of the transmitting circuitthrough conductor S2 is open at arming switch A82 and no direct voltagefrom battery BI through indication relays A2 and MK2 is applied to tube96 to break down the tube and hence no indication current flows tooperate indication relays A2 and MK2 associated with mine M2. Atdistribution point DP2 the filter MF is tuned to pass periodic currentof the frequency f2, and hence electron tube 99 of receiving device R5is excited. Since mine M5 i assumed to be armed, direct voltage frombattery BI is applied to anode [M of tube 99 and tube 99 breaks down topermit indication current to flow, the circuit extending from terminal Bof battery BI through 3N contact of relay K, winding of indication relayA5, top winding of indication relay MK5, front contact I99 of relay I,wire I85, front contacts 98 and 85 of relays 2 and CO, respectively,conductor L2, anode NH and tube space to cathode I92 of tube 99, fuse59, conductor S5, impedance I93, detonator D5, contact 59--69 of switchASS, ground path between electrodes I94 and 39 and 4N contact of relay Kto terminal C. This indication current is sufficient to operate relaysA5 and MK5 but is not suificient to fire detonator D5. The closing ofcontact IN of relay MK5 completes an obvious circuit for lamp LME toilluminate that lamp as an indication that mine M5 is armed. Operationof relay MK5 to the left also prepares a circuit for firing mine M5 aswill shortly appear. The function of relay A5 will be pointed out later.

The release of relay I at the start of thi step of the operation cyclecauses an operation of relays T, Y, ZI and Z2. Release of relay I toopen front contact 8'! deenergizes relay T, and relay T immediatelyreleases to open front con tact I3 and close back contact 64 and shiftthe circuit through relay X from the lower windings of relay ZI and Z2to the lower winding of relay Y, and relay Y is operated to the left.When relay Y is operated to the left, relay T is reenergized over thecircuit completed at back contact 1| of relay W, 3N contact of relay Y,wire I55, front contact I95 of relay 2 and wire I66. The picking up ofrelay T to open back contact 64 and close front contact 13 shifts thecircuit through relay X from the lower winding of relay Y to the topwindings of relays Z! and Z2.

Relays ZI and Z2 are now operated to the left to start the next step ofthe operation cycle. Operation of relay Z2 to the left to open its 2Rcontact deenergizes rela CO and that relay releases at once to removeoscillator CS2 and bat tery BI from the transmitting circuits,permitting the corresponding receiving devices and indication relays tobecome deenergized. W'hen relay ZI operates to the left to open its 3Rcontact, relay 2 is deenergized and releases at the and relay 3 pickedup, relay CO is reenergized by the circuit including IN contact of relayZ2, wire I68, back contact I08 of relay 2 and front contact I99 of relay3. With relays 3 and, CO picked up, the oscillator CS3 and battery BI inseries with the indication relays for the third mine of each group areconnected to the transmitting circuits. The connection of oscillator OSI to conductor LI is completed, through wire I'M, condenser I15, frontcont-act I III of relay 3 and front contact 8| of relay CO; and theconnection to conductor L2 is completed through wire I'I I, condenserI16, front contact I II of relay 3 and front contact of rela CO. Thefilters of receiving devices R3 andR6 are the ones tuned to pass currentat the i3 frequency, and hence the associated electron tubes areexcited. Since mines M3 and M6 are not at this time armed, no directvoltage from battery BI is applied to the devices R3 and R6, and noindication current flows to energize the indication relays associatedfor mines M3 and M6,

Release of relay 2 at the start of this step of the operation cycle,causes an operation of relays T, Y, ZI and Z2. Relay T is deenergized,due to the opening of front contact I of relay 2, and relay T uponreleasing shifts the circuit through relay X from the top windings ofrelays ZI and Z2 to the top Winding of rela Y, and relay Y is operatedto the right. Rela T is now reenergized over the circuit including 3Rcontact of relay Y, wire I'II, front contact II 2 of relay 3, and wireI66, and relay T on picking up shifts the circuit through relay X fromthe top Winding of relay Y to the lower windings of relays ZI and, Z2.

Relays ZI and Z2 are now operated to the right to start the next step ofthe operation cycle. When relay Z2 is operated to the right to open itsIN contact, relay CO is deenergized and immediately releases to removeoscillator CS3 and batter BI from the transmitting circuits. With relayZI operated to the right to open its 4N contact, relay 3 is deenergizedand releases at the end of its slow release period. During this slowrelease period of relay 3, the next relay 6 of the s pp in s nergized bycurrent flowing from terminal B through the 2N contacts of relays K andX, 3R contact of rela ZI, wire IBI, front contact H3 of relay 3, INcontact of relay CR, and winding of relay 6 to terminal C. Rela 6 is thefinal rela of the stepping relays, since as stated hereinbefore, onlythree mines of each group of mines are shown. It is evident, I believe,that more than three mines can be included in each group, and theadditional mines selectively indicated and controlled by providingadditional oscillators to supply periodic currents of differentfrequencies and by providing additional relays in the stepping chain ofrelays, there being provided one additional stepping relay for eachadditional mine of each group. There would also. be provided, of course,additional indication relays. The additional stepping relays would besuccessively operated in the manner similar to the oper- 'ation ofrelays I, 2 and 3 to successively connect the additional oscillators andindication relays to the transmitting circuits.

The picking up of relay 6 of the stepping relays, starts the firingportion of the operation cycle. When relay 3 releases at the end of'theindication portion of the operation cycle, the relay CR is operated tothe right by energy supplied from terminal B through 2N contacts ofrelays K and X, 3R contact of relay ZI, wire I6I, lower Winding of relayCR, front contact II4 of relay 6 and Winding of relay 6 to terminal C.With rela CR operated to the right, the firing power relay FF isprovided with the followingcircuit, terminal B, 2R contact ofrelay Y,wire I I8, front contact II5 of relay 5, 2R contact of relay CR, contactIIS of a two-position switch AP and winding of relay F? to terminal C.Operation of rela CR to the right to open its 3N contact de'energizesrela I, and relay I releases at once to disconnect all indicationrelays, but the relays MKI and MK5 still remain at their normalpositions so that lamps LMI and LM5 continue to be illuminated. Relay COis now energized by current supplied from terminal B through 2R contactof relay Z2, wire I12, back contact I I! of rela 3 and front contact N8of relay 8. With indication relays MKI and MKE operated to the left andrelay CQ picked up, oscillators OSI and 052 are connected to thetransmitting circuits to excite the receiving devices of the armedmines, oscillator OS! be-- ing connected to conductor LI over wire I8,2N contact of relay MKI, front contact H9 of relay W and front contact8I of relay CO; and oscillator S2 being connected to conductor L2 overwire 93, 2N contact of relay MK and front contacts I28 and 85 of relaysFP and CO, respectively Periodic current from oscillator OSI excitestube 2| of receiving device RI and periodic current from oscillator 0S2excites tube 99 of receiving device R5 in the manner already explained'Simultaneously with this exciting of tubes 2I and 99, the batter B2 isconnected to the anode of these tubes over the transmitting circuits,the circuit for tube 2I extending from the positive terminal of batterB2 through a winding of biased polar relay LK, front contact I2l ofrelay FP, impedance I22, front contact 8! of relay CO, conductor LI,anode 35 and tube space to cathode 33 of tube 2|, the circuit extensionto mine MI, and ground path between electrodes 32-and I23 to thenegative terminal of battery B2. The circuit for tube 89 extends from,

the positive terminal of battery B2 through the winding of relay LK,front contact I24 of relay FP, impedance I25, front contact 85 of relayCO, conductor L2, anode IDI and tube space to cathode IE2 of tube 99,the circuit extension to mine M5 and the ground path between electrodesI04 and I23 to the negative terminal of battery B2. The voltage ofbattery B2 breaks down tubes 2I and 99 and instantly fires detonators DIand D5 of mines MI and M5. From the foregoing description and from'aninspection of the drawings it is evident that additional mines, ifarmed, would be automatically and instantly fired.

The apparatus when set for automatic operation is locked at the firingstep of the operation cycle until all armed mines are fired and thefuses at the'distribution points for the fired mines are blown. It is tobe noted that when relay 3 is released and relay 6 is picked up at thestart of the firing portion of the operation cycle, the relay Tisenergized over a circuit completed at back contact II of rela W, 3Rcon-tact of relay Y, wire Il'I, front contact I56 of relay 8, 2R contactof relay LK and Wire I66. As firing current flows relay LK is operatedto the left to open its 2R contact and relay T is deenergized andreleased to shift the circuit through relay X from the lower windings ofrelays ZI and Z2 to the lower winding of relay Y; This causes relay Y tobe operated to the left, so that relay T will not be reenergized untilrelay LK is operated back to its reverse position by its bias and againcloses its 2R contact, the circuit for relay T being then completedthrough back contact II of relay W, 3N contact of relay Y, wire I65,front contact I25 of relay I5, contact I3I of switch 4P, 2R contact ofrelay LK and wire I66, Relay LK cannot be operated back to its biasedposition until the armed mines are fired, and the fuses blown, for assoon as a mine is fired, the mine cable S be comes grounded and currentcontinues to flow from battery B2 through rela LK until thecorresponding fuse blows. As soon as the armed mines are all fired andthe cables S disconnected from the distribution points b the blowing ofthe corresponding fuses, then current from battery B2 ceases and relayLK is operated to its biased position. It is to be noted that when relayY is last operated to the left, the circuit for relay FP was opened at2R contact of relay Y, but that relay FP is retained energized by astick circuit including terminal E, IN contact of relay LK, frontcontact I26 and Winding of relay FF, and terminal C. Operation of relayLK at the end of the firing of the mines thus released rela FP todisconnect all oscillators as well as the firing battery B2 from thetransmitting circuits. Operation of relay LK to its bias position toenergize relay T over the circuit previously traced causes relay T topick up to shift the circuit through relay X from the lower winding ofrelay Y to the top windings of relays ZI and Z2, and relays Z! and Z2are operated to the left. With relays ZI and Z2 operated to the left,both relays 6 and C0 are deenergized and released, relay 6 releasing atthe end of a predetermined slow release period, but relay CO releasingat once. This terminates the firing portion of the operation cycle and.starts a disarming portion.

Firing of a mine produces shocks that may ar an adjacent mine and theoffice control apparatus functions to disarm such armed mines. Whenrelays Z'I and Z2 operate to left, as explained above, to deenergizerelays 6 and CO and complete the firing portion of the operation cycle,relay I is again energized by a circuit including 2N contacts of relaysK and X, 4N contact of relay ZI, wire I 6'! and front contact I32 ofrelay 6. Release of relay 6 completes a circuit for reset relay RS, suchcircuit extending from terminal B through back contact 61 of relay W,wire I52, 3R contact of relay CR, back contact I33 of relay 6 andwinding of relay RS to terminal 0. With relay I picked up and relay 6released, relay CO receives energy from terminal B through IN contact ofrelay Z2, wire I 68, back contact I34 of relay 6, front contact I! ofrelay I and winding of relay CO- to terminal C. Relays I and C0 are nowpicked up to connect oscillator OSI to the transmitting circuit, theconnection to conductor LI of the first transmitting circuit beingcompleted at front contacts and 8! of relays I and CO, respectively; andthe connection to conductor L2 of the second transmitting circuit beingcompleted at front contacts 84 and 85 of relays I and CO, respectively.Current from oscillator OSI now serves to excite the tubes of thereceiving devices RI and R4 in the manner already explained. With resetrelay RS picked up, winding I84 of transformer TI, the source of 60cycle alternating current, is connected to the transmitting circuits,the connection to conductor LI of the first circuit being completed atfront contact I35 of relay RS, condenser I19 and front contact 8| ofrelay CO; and the connection to conductor L2 of the second transmittingcircuit being completed at front contact I35 of relay RS, condenser I80and front contact 85 of relay CO. At distribution point DPI this 60cycle alternating current accomplishes nothing in the way of ionizingtube 2I, because mine MI has been fired. At distribution point DP2,,the60 cycle current applied to the anode of tube 86 causes that tube to beionized and positive half cycles of the 60 cycle current are suppliedthrough filter FT4 at mine M4 to relay'MR l and relay MR4 is energizedto reset arming switch ASA in the event the mine has been armed due tothe shock of firing mine M5.

Relay T is deenergized when relay 6 is released to open front contactI25 and relay T upon releasing shifts the circuit through relay X fromthe top windings of relays ZI and Z2 to the top winding of relay Y, andrelay Y is operated to the right so that relay T is reenergized over-thecircuit including 3R contact of relay Y, wire III and front contact 8'!of relay I. Relay .1 on picking up shifts the circuit through relay Xfrom the top winding of relay Y to the lower windings of relays ZI andZ2 and these latter relays are operated to the right. The operation ofrelay Z2 to the right to open its IN contact deenergizes relay CO andrelay CO immediately releases to disconnect the oscillator OSI andtransformer TI from the transmitting'circuit's. Relay MR4 of mine M4 inow deenergized and the mine is dis armed. Operation of relay ZI to theright to open its 4N contact deenergizes relay I, and relay I isreleased at the end of its slow release period. Relay 2 is energizedduring the slow release period of relay I, the circuit for relay 2including the 3R contact for relay ZI, wire I! and front contact 88 ofrelay I. With relay I released and relay 2 picked up, the relay CO isreenergized by means of the circuit completed at back contact 9| ofrelay I and front contact 92 of relay 2, and with relays 2 and CO pickedup the oscillator CS2 is connected to the transmitting circuits, theconnection to conductor LI being completed at front contact 95 of relay2 and front contact SI of relay CO, and the connection to conductor L2being completed at front contact 98 of relay 2 and front contact 85 ofrelay CO. Since reset relay RS is still energized, the transformer TI isalso connected to the transmitting circuits through the connectionsexplained hereinbefore. Periodic current from oscillator OS2 and 60cycle alternating current from transformer TI are now delivered to thedistribution points. At distribution point DPI tube 96 is excited andbreaks down so that current is delivered to relay MR2 of mine M2 andthat relay energized to reset the arming switch AS2 in the event mine M2has become armed due to the shock of firing the adjacent mine MI. Atdistribution point DPZ nothing happens because mine M5 has been fired.The control means at the office automatically continues to successfullyoperate the stepping relays in the manner explained during theindication portion of the operation cycle, and the oscillators areconnected one at a time to the transmitting circuits, transformer TIbeing connected to the circuits simultaneously with each oscillator. Itfollows that each receiving device at the distribution points will beexcited and the MR relay of the corresponding mine energized and thendeenergized to disarm any armed mine. It should be noted that duringthis disarming portion of the operation cycle, the relay I remainsreleased and all indication relays are disconnected from thetransmitting circuits. When relays ZI and Z2 are operated to th right atthe completion of the last disarming step, the control apparatusautomatically restores to its normal or alert condition in the followingmanner. of the operation cycle, relay I2 is energized, current beingsupplied to relay I2 by a circuit extending from terminal B through 2Ncontact of relay K, 2N contact of relay X, 3R contact of relay ZI, WireIBI, front contact II3 of relay 3, IR contact of relay CR and Winding ofrelay I2 to terminal C. Relay I2 now picks up and provides a stickcircuit for itself at its own front contact I31, When relay 3 isreleased at the end of its slow release period, the opening of frontcontact I I 2 causes relay T to be deenergized and released to shift thecircuit through relay X from the lower windings of relays ZI and Z2 tothe lower winding of relay Y, and relay Y is operated to the left. Nowwith relay I2 picked up and relay T released, the relay K receivescurrent from terminal B through front contact I38 of relay I2, wire I8I,back contact I39 of relay T, front contact I40 of relay WP, since relayWP is now picked up, and lower winding of relay K to terminal C. Thisoperates relay K back to its reverse position to open the circuit forrelays X, Y, ZI and Z2. Relay X being of the biased polar type, itoperates to its bias reverse position, while relays Y, ZI and Z2 remainat the position to which they were last moved. Thecircuit for thestepping relays is'now opened at contact 2N of'relay K, and the circuitsfor relays W and WI are closed at the IR and 2R contacts of relay K.Relay W on picking up to open back contacts 6'! and deenergizes relays'RS and WP, relay RS releasing at once and relay WP releasing at the endof a predetermined slow release period. Operation of relay K to closeits 3R and 4E contacts connects battery BI to the transmitting circuitsat its normal polarity so that the LL and LP relays at each distributionpoint are reenergized. The sudden increase of flow of direct currentthrough relays LLI and LPI at diStIibllIliOIfpOiI'lt DPI causes anelectromotive force to be induced in winding 6| of transformer T2, andrelay KI is momentarily operated to close its IN contact. Similarly,relay K2 is operated to close its IN contact due to the electromotiveforces induced in transformer T3 due to the flow of current through theLL2 and LP2 relays at distribution point DPZ. Relay K however, is notoperated by this momentary operation of relays KI and K2 because thecircuit for the top winding of relay K is held open at back contact 62of relay WP, relay WP being provided with a slow release periodsufficiently long that it is not released until after relays KI and K2are operated back to their biased positions. When relay WP subsequentlyreleases the apparatus is restored to its alert conditions. It is to beobserved that the indication relays MKI and MK5 corresponding to thefired mines MI and M5 remain at their normal positions causing thecorresponding indication lamps to continue to be illuminated.

In the event other mines are now armed due to a vessel coming in contacttherewith, the control apparatus automatically functions to indicate thearmed mine, fire the armed mine, disarm mines that become armed due tothe shock of firing the armed mine, and then restore itself to the alertcondition by an operation cycle similar to that described hereinbefore.Such cycle of operation will be repeated as long as there remains anymine of a field to be fired.

At the end of the disarming portion.

Under automatic operation of the apparatus provision is made whereby twoadjacent mines,

one on either side of a contacted mine, are automatically fired, ifdesired, when the contacted mine is fired. This is accomplished asfollows: Assume that the operator has actuated push button l? to closecontact i4! and mine M2 has been contacted by a vessel and an operationcycle, similar to that already described, has progressed to the pointwhere the indication relays A2 and MK2 are operated to their normal.positions so that lamp LM2 is illuminated to indicate the armedcondition of mine M2. Energy is nowapplied to the lower Winding of eachindication relay MK! and MK3 for the mines MI and M3, the circuit forrelay MKI being completed from terminal B through contact Ml of pushbutton iP, IN contact of relay AZ and lower winding of relay MKI to amid terminal BL of battery BI; and the circuit for relay MK3 being thesame as that traced for relay MKI up to push button [P and thencethrough the 2N contact of relay A2 and the lower winding of relay MK3 toterminal BL. Both relays MKI and MK3 are now operated to close theirrespective 2N contacts so that oscillators OSI and 083 are connected tothe transmitting circuit along with oscillator S2 during the firingportion of the operation cycle, with the result that mines MI and M3 aresimultaneously fired withmine M2. In connection with firing mines MI andM3 with mine M2, it is considered that arming switches ASI and A83 areactuated to arm mines Ml and Then by manual operation of a push buttonor firing switch the cycle of operation is permitted to continue. Thisautomatically fires the selected mines and then disarms all those mineschat were armed due to the shock of firing the selected mines. a

Underserni-automatic operation, the apparatus is at its alert conditionand the firing switch 4? is set to open its contacts I I8 and I l 3.When a mine 'or mines are contacted by a vessel, the operation cycle ofthe control apparatus similar to that explained under automaticoperation is'initiated to indicate the contacted mine and such operationneed not be repeated. This operation cycle continues until relay 3releases and relay picks up to start the firing portion of the operationcycle. Firing relay FF is not supplied with energy because contact H5 ofswitch 41? is open and relay LK remains at its bias position because nofiring current flows with the result that relay T is held energized bythe circuit completed through back contact I! of relay W, 3R contact ofrelay Y, wire I'H, front contact I56 of relay 5, 2R contact of relay LKand wire H36, and further progression of the operation cycle is stopped.The contacted mines are indicated by the respective indication lamps.The operator when ready closes the firing switch AP and the operationcycle then progresses to fire the contacted mine, disarm mines that arearmed due to the shock and then the apparatus is restored to its normalalert condition, this part of the operation cycle being the same as thatdescribed for automatic operation. I shall now assume that undersemi-automatic operation mine MI is contacted andthe control apparatusoperates to the firing portion,

leaving lamp LMI illuminated to indicate the contacted mine Mlyand thatthe operator desires to fire mine M2 along with mine MI The operatorwould actuate a push button 2AB (see upper left-hand portion of Fig. a).Operation of push button 2AB completes a circuit from terminal B throughpush button 2A3 and the lower winding of indication relay MK2 toterminal BL, and relay MK2 is operated to the left. Operation of relayMK2 to the left to close its IN contact causes lamp LM2 to beilluminated, and the closing of contact 2N of relay MK2 prepares thecircuit by which oscillator CS2 is connected to the trans mittingcircuit during the firing portion of the operation cycle. The operatornow closes switch 4P to permit the progression of the operation cycle ofthe control'apparatus, with the result that mine M2 would be fired alongwith mine Ml, assuming of course that the shock of firing mine Ml causesmine M2 to become armed. If the operator desired to fire additionalmines, he would actuate the AB push button of such mines as he desiredto fire. In the event some of the additional mines selected bytheoperator are so far removed from the contacted mine that they wouldnot be armed by the shock of firing the contacted mine, the operatorwould actuate a push button 5P previous to the closing of switch 45. Theclosing of push button 5P energizes relay RS over an obvious circuitincluding contact I42 of push button SF. The firing switch 4P is nowmoved to its closed position and the control apparatus continues theoperation cycle and with relay RS- picked up 60 cycle alternatingcurrent is supplied to the transmitting circuits and. passed by thereceiving devices excited by the periodic current supplied by theoscillators so that 'the'MR relays of such mines as have been selectedare energized to arm the mine. Current of 600 volts supplied by batteryB2 is eifective to fire all the armed mines; If the operator desires todisarm some mine that has become armed through the contact by a vessel,he can do so by actuating a can-,

celin'g push button CB. For example, assuming mines MI and M2 havebecome armed due to contact by a vessel, and the operation cycle hasprogressed to illuminate lamps LMI and LM2, the operation cycle stoppedat the firing portion of the cycle and the operator wishes to disarmmine MI and allow mine M2 to be fired, he would actuate a canceling pushbutton ICB (see upper left-hand portion of Fig. 1a). button ICBcompletes the circuit for energizing the lower winding of, indicationrelay l MK, relay IMK having previously been operated to its normalposition during the indication portion of the operation cycle. Closingof push button ICB permits current to fiow from mid terminal BL ofbattery Bl through lower winding of relay IMK and the contact of pushbutton ICE to terminal C of battery BI, and current flows in relay IMKin the direction to operate the relay to its reverse position to openits 2N contact by which oscillator OSI is connected to the transmittingcircuit. The operator would then close the firing switch 4P to continuethe operation cycle of the control apparatus and only mine M2 would befired. In like'manner operation of any of the other canceling pushbuttons CB associated with the dif- Closing of push ferent indicationrelays serves to cancel armed mines.

When the system is set for manual operation any mine may be fired at anytime, regardless of-whether or not it has been contacted by a vessel, byfirst actuating a manual firing switch and then closing the "armingpush'button AB for the mine to be fired. For manual operation,

the control means is made non active by twoposition switch 2P being setto open contact 31 and close contact I43. The opening of contact 31deenergizes relay W and removes current from relays X, Y, ZI and Z2 andprevents any automatic operation of the stepping relays. The closing ofcontact I43 of switch 2P operates relay K to the left, current beingsupplied duringthe slow release period of relay W from terminal Bthrough contact I 43, top winding of relay K, front contact I9 of relayW and back contact 62- of' relay WP to terminal C. Operation of relay Kto the left releases relay WI to open the connections from battery BIthrough transformers TI and T3 to the transmitting circuits.

For manual operation, a firing switch BP is set to close its contactsI44, I45 and I46 and current is supplied by obvious circuits to relaysCO, RS and FF. With these relays picked up battery B2 and transformer TIare connected to the transmitting circuits by circuit connectionspointed out hereinbefore. If now the arming push button IAB, forexample, is closed, the corresponding indication relay MKI is operatedto the left to close its 2N contact and oscillator OSI is connected tothe transmitting circuit extending to distribution point DPI to excitethe receiving device RI so that 60 cycle ci'urent is passed to mine MIwhere it energizes relay MRI to arm the mine, and 600 volt directcurrent from battery B2 flows through receiving device RI and thedetonator DI to fire the mine. Any of the other mines can be fired in asimilar manner by actuating the corresponding AB push button. When thedesired mines have been fired manually and further manual operation isnot desired, the apparatus can be set for either automatic operation orsemi-automatic operation by restoring switches 2P and GP to their normalpositions. The operation of switch GP to its normal open positiondeenergizes relays 00, RS and FF to disconnect all current sources fromthe transmitting circuits. The closing of contact 37 of switch 2Psupplies current from terminal B through contact 31, contact I41 of apush button 1P, 3R contact of relay X, front contact I40 of relay WP andlower winding of relay K to terminal C, and relay K is operated to itsreverse position, causing in turn the relays W and WI to be picked upwith the result that the apparatus is restored to its alert conditionWhen mines are fired manually and adjacent mines are armed by the shock,such adjacent mines can be disarmed after the alert condition isrestored, by operation of push buttons IP and 3P, switch 4P being at itsopen position. The closing of contact I48 of push button 1P causes relayBG to .be energized over an obvious circuit and the closing of contactI49 of push button 1P completes the previously traced circuit for relayK to operate relay K to the left. This operation of relay K deenergizesrelays W and WI and initiates an operation cycle of the stepping relaysimilar to that described under full automatic.

control. Relay I is now deenergized however because contact 69 of pushbutton 3P is open and relay I upon being released disconnects theindication relays from the transmitting circuits while the steppingrelays are progressively operated. Relay RS is energized, however, overa circuit including terminal B, back contact 51 of relay W, frontcontact I50 of relay BG, wire I82 and winding of relay RS to terminal C.With relay RS picked up, transformer TI is connected to the transmittingcircuits as previously explained. Thus, as the stepping relays I, 2 and3 are picked up during the operation cycle, and the oscillators OSI, OS2and 083 are connected to the transmitting circuits, the electron tubesof the various receiving devices become excited and are ionized due tothe presence of the 60 cycle current, with the result that energy ispassed to the various mines to energize the respective MR relays, andany mine that has become armed due to shock of a fired mine is disarmed.Since switch 4P is open, the operation cycle is stopped at the end ofthe indication portion.-

The apparatus restores to the alert condition when push buttons SP andII are reclosed. The opening of contact I48 of push button IP opens thepick-up circuit of relay BG but relay BG is now retained energized overa stick circuit including front contact I52 of relay WP and frontcontact I53 of relay BG. Relay K now receives energy from terminal Bthrough contacttl of switch 2?, contact I54 of switch 'IP, front contactI55 of relay BG, front contact MD of relay WP and lower winding of relayK to terminal C, and relay K is operated to the right. This operation ofrelay K deenergizes relay X and in turn relay 6, and reenergizes relaysW and. WI. The picking up of relay W opens back contacts 61 and causingrelays RS and W? to be deenergized. The picking up of relay WI to closefront contacts 43 and 53, connects battery BI to the transmittingcircuit 50 that the LL and LP relays at each distribution point areenergized. Relay WP releases at the end of its slow release period toopen front contact I52 and deenergize relay BG, with the result that thesystem is restored to its normal alert condition.

Provision has been made for testing each mine to see that everythin isin proper working condition. In order to test the equipment of a minethe firing'switch 4P would be open and testing switch 'IP set to closecontact I48 nd I49. Closing of contacts I48 and I49 energizes relayBGand operates relay K to the left as explained hereinbefore. Thisoperation of relay K releases relays W and WI and the apparatusautomatically progresses through its operation cycle in the mannerexplained hereinbefore up to the picking up of relay 6 at the start ofthe firing portion of the cycle. This operation of relay K alsodeenergizes the LL and LP relays at the distribution points. During theprogressive operation the oscillators OSI, OS2 and CS3 are connected oneat a time to the transmitting circuits, and the receiving devices at thedistribution points are in turn excited. Since relay RS is nOW picked upover the circuit including front contact I50 of relay BG and relay I isenergized in the usual mannenthe 60 cycle alternating current fromtransformer TI and the respective indication relay MK in series withbattery BI are connected to the transmitting circuits simultaneouslywith the connecting of each oscillator to the transmitting circuits. Asthe various receiving devices are excited, the 60 cycle current isapplied to the anode of the respective tube causing current to be passedthrough the tube to the respective mine, and the respective MR relay ispicked up to close the respectivc arming switch A55, The closing of eacharming switch completes the circuitjpath through the detonator with theresult thatacurrent'from battery Bl flows through the indication relays.MK and the detonaton. It is to be observed that the current from batteryBl through the indication relays and the individual detonators is of avalue insufiicient to fire the mine,'but is sufiicient to operate theindication relays. operationv of each indication relay MK to the-left isa check that the circuits for the corresponding mine are all intact. Ifthe system is functioning properly, the indication relay MK for eachmine in the entire field would be operated to cause all by operation ofthe respective canceling push button CB;

Apparatus here disclosed has the advantages that automatic indicationatv the control point of the contacting and arming of any or all minesof a mine field is effected, automatic or semi-automatic firing of anyor all the contacted mines is provided, automatic firing of other minesin addition to the contacted mine may be effected,

semi-automatic firing of any number of mines inaddition to the onescontacted may be accomplished, manually firing of all or any of themines of the entire field whether contacted or not may be accomplished,automatic disarming of all mines that are armed as a'result of firingadjacent mines is provided, periodic testing of the equipment of eachmine may be accomplished without.

firing the mine, and the several functions are all accomplished by asingle two-conductor transmitting circuit for each group of mines.

Although I have herein shown and described only one form of selectivecontrol and indication system embodying my invention, it is understoodthat various changes and modifications may be made therein within thescopeof appended claims without departing from the spirit and scope ofmy invention.

Having thus described my invention, what I claim is:

1. In combination, an office, and a remote point connected by atransmitting circuit which is normally excited by an office source ofdirect current of a preselected low voltage, an office source ofoscillating current of a preselected frequency, an oifice source ofdirect current of a preselected high voltage, an office source ofcurrent of a preselected particular characteristic, normally in riodiccurrent source and said particular characteristic current source to thecircuit, a circuit controller having a normally open contact whichbecomes closed in response to a predetermined event, a circuit pathincluding said contact connected across said circuit at said remotepoint to create an increase in the flow of direct current in saidcircuit when the contact becomes closed; of-

The

fice means connected to saidcircuit energized by such increase of directcurrent to initiate opera,

tion of said control means, receiving relay means at said pointconnectedto said circuit and energized' only by current of saidpreselected frequency, an; operating'element which is operated only bycurrent of said high voltage connected to said circuit by said receivingrelay means when energized, andreset relay means energized only bycurrentof said particular characteristic and connected to said circuitby said receiving relay means when energized for restoring said contactto its open position.

2. In combination, an oflice and a'remote point connected by atransmitting circuit which is normally excited b .an office source ofdirect current to energize a-remote point relay connected across thecircuit; anoffice source of oscillating current of apreselectedfrequency, an'office indioationrelay, normally inactiveofiice control means oper'-' able to'connect said source of oscillatingcurrent to said circuit and to interpose-said indication re lay in theconnection of said direct current source to the circuit, an electricalequipment having a normally open contact which becomes closed inresponse to a predetermined'event, a shunt path including a frontcontact of said remote point relay and said controller contact to shuntsaid circuitj toreleasesaid remote point relay and to create a momentaryincrease in the flow of current in said circuitwhen said contact becomesclosed, office means connected to said circuit energized by suchincrease in the flow of direct cur-.

rent to initiate operation of said control means, and receiving relaymeans at said point connected to, said circuit and energized only bycurrent of said preselected frequency to connect said controller contactacross said circuit independently of said remote point relay forenergizing said indication relay when the controller contact is closed.I

3. Incombination, an office and a remote point connected by atransmitting circuit which is normally excited by an office source ofdirect current to energize a remote point relay connected across thecircuit, an 'officesourceof oscillating current of a preselectedfrequency, an ofiice source of operating current of 'a preselected highvoltage, normally inactive ofiice control means operable to connect saidoscillating current source and said operating current source to saidcircuit, an electrical equipment having a normally open controllercontact which becomes closed in response to a predetermined event and anoperatingelement which is operated only when "supplied with current, ofsaid preselected high voltage, receiving relay means at'sai'd pointconnected to said circuit and energized only by current of saidpreselected frequency, a first circuit path across said circuit andincluding a front contact of said remote point relay and said controllercontact; a second circuit path across said circuit including saidcontroller contact, said operating element and an element madeconductive only when said receiving relay means is energized; 'saidfirst circuit path to shunt saidcircuit when said controller contact isclosed to release said remote point relay and to create an impulse ofdirect current in said circuit, an office means connected to saidcircuit energized. by such impulse of direct current to initiateoperation of said control means for operation of said operating elementdueto said second circuit path. e

4. In combination, an office and aremote point connected by atransmitting circuit which is nor mally excited by an office source ofdirect current, a plurality of equipments associated with said remotepoint each having a normally open contact which becomes closed inresponse to a predetermined event individual to the equipment, aplurality of oflice sources of periodic currents of difiere'ntfrequencies with a difierent source assigned to each equipment, aplurality of receiving devices one for each of said equipments, saiddevices connected in multiple to said circuit at said remote point, eachsaid device energized only by current of the frequency of the periodiccurrent source assigned to the associated equipment, normally inactiveofiice control means operable to selectively connect the periodiccurrent sources to said circuit, relay means at said remote pointcontrolled by said controller contacts to cause an impulse of directcurrent to flow in saidcircuit when any one of the controller contactsis closed, ofiice means connected to said circuit energized by suchimpulse of direct current to initiate operation of said control means,and operating means for each of said equipments rendered active by theassociated receiving device when energized.

5. In combination, an'ofiice and a remote point connected by atransmitting circuit which is normally excited by an ofiice source ofdirect current, a plurality ofequipments associated with said remotepoint each having a normally open controller contact which becomesclosed in response to a predetermined event individual to the equipment,a plurality of office sources of periodic currents of differentfrequencies with a different source assigned to each equipment, aplurality of receiving devices one for each of said equipments, saiddevices connected in multiple to said circuit at said remote point andeach said device energized only by current of the frequency of theperiodic current source assigned to the associated equipment, aplurality of ofiice indication means one for each of said equipments,normally inactive office control means operable to successively connectsaid periodic current sources and indication means to said circuit withthe source and indication means for each equipment simultaneouslyconnected to the circuit, relay means at said point controlled by saidcontroller contacts to cause an impulse of direct current to flow insaid circuit when any one of said contacts is closed, ofiice meansconnected to said circuit energized by such impulse of direct current toinitiate operation of said control means, and means governed by eachreceiving device to complete a path across said circuit through thecontroller contact of the associated equipment to energize theindication means of the same equipment by said direct current source.

6. In combination, an office and a remote point connected by atransmitting circuit which is normally excited by an ofiice source ofdirect current, a plurality of sources of periodic currents of differentpreselected frequencies, a plurality of office indication relays therebeing a, relay associated with each periodic current source, normallyinactive ofiice control means operable to connect in a step-by-stepmanner the periodic current sources and indication relays to saidcircuit with an associated source and relay simultaneously connected,receiving devices one associated with each periodic current source andconnected to said circuit in multiple at said point, each receivingdevice energized only by current of the frequency of the respectivesource, electrical equipments one associated with each receiving device,each equipment provided with a normally open contact which becomesclosed in response to a predetermined event, relay means at said pointconnected to said circuit and governed by said contacts to create amomentary flow of direct current in said circuit when any one of thecontacts becomes closed,-oilice means connected to said circuitenergized bysuch momentary fioW ofgcurrent in initiating an operation ofsaid control means, and means governed by each receiving device and thecontact of the associated equipment tocondition said circuit to energizethe associated indication relay by said direct current source.

7. In combination, an ofliceand a remote point connected by atransmitting circuit Which isnormally excited by an office source ofdirect current of a preselected low voltage, a plurality of ofiicesources of periodic currents of difierent frequencies, an office sourceof direct current of a preselected high voltage, a normally inactiveoffice control means operable to connect said highvoltage source andpreselected onesv of the periodic current sources to the circuit,receiving'devices one associated with each periodic current sourceconnected to said circuit in multiple at said remote point, eachreceiving device energized only by current of the frequencyv of theassociated source, electrical equipments one for each receiving device,each said equipments including an operating element which is operatedonly by current of said high voltage and a contact which becomes closedin response I to a predetermined even-t, relay means at said pointconnected to said circuit and governed by saidcontacts to create amomentary flow of current in said circuit when any one of said contactsbecomes closed, office means connected to said circuit energized by suchmomentary flow of currentto initiate an operation of said control means,and circuit means governed by each receiving device and the contact ofthe associated equipment to connect the operating element of the sameequipment to said circuit for operation of the element by currentsupplied by said high voltage direct current source.

8. In combination, an oifice and a remote point connected by atransmitting circuit which is normally excited by an ofiice low voltagesource of direct current, a control relay at said point connected tosaid circuit to be energized by said low voltage source of directcurrent, a group of mines each provided with a normally open armingswitch and a detonator which when supplied with current of a preselectedhigh voltage fires the mine, a circuit extension for each mine includingthe respective detonator and arming switch, each said circuit extensionsconnected to said circuit through a front contact of said control relay,receiving devices one for each mine and connected in multiple to saidcircuit at said point, each such device energized only by periodiccurrent of a frequency preselected for the individual device, eachdevice when energized to comiect the circuit extension of the respectivemine to said circuit independent of said control relay, ofiice sourcesof periodic currents one for each mine and each source'of the frequencypreselected for the receiving device of the same mine, an'oflice sourceof direct current of said high voltage, normally inactive office controlmeans operable to connect said high voltage source and preselected onesof said periodic current sources to the circuit, and ofiice meansconnected to said circuit energized to initiate operation of saidcontrol means in response to the impulse of direct current created insaid circuit due to said low' voltage current source when an armingswitch is closed.

9. In combination, an office and a remote point connected by atransmitting circuit which is normally excited by an ofiice low voltagesource of direct current, a control relay at said point connected tosaid circuit to be'energized by said low I voltage source of directcurrent, a group of mines said circuit through a front contact of saidcon-e trol relay, receiving devices one for each mine and connected inmultiple'to said circuit'at said point, each such device energized onlyby periodic current of a frequency preselected for the individualdevice, each device when energized to connect the circuit extension ofthe respectiv mine to said circuit independent of said control relay,officesources of periodic currents one for each mine and each source ofthe frequency preselected for the receiving device of the same mine, anoffice, source of direct current of said high voltage, ofiice indicationrelaysone for each of said mines, normally inactive oflice control meanshaving an operationcycle comprising an indication portion to connectstep-by-step the periodic current sources and indication relays to saidcircuit to energize the indication relay of any mine whose arming switchis closed and a firing portion to connect the periodic current sourcesand said high voltage current source to said circuit to fire any minewhose arming switch is closed, and oflice means connected to saidcircuit energized to initiate an operation cycle of said control meansin responseto the low voltage impulse of direct current created in saidcircuit when an arming switch is closed.

, 10, In combination, a plurality of mines each of which is providedwith an arming switch and a detonator, a transmitting circuit between adistribution point and a remote office, a circuit extension for eachmine connected to said transmitting circuit at said point and includingthe respective detonator and arming switch, an oflice source of directcurrent connected to said transmitting circuit, a control relayconnected to the circuit at said point to be energized by said source ofdirect current, said control relay having a front contact interposed ineach of said circuit extensions, selective means including ofiicesources of periodic currents of different frequencies and.

receiving devices connected across said transmitting circuit at saiddistribution point there being a preselected source and device assignedto each mine and each device energized only by current of the frequencyof the respective source, normally inactive oflice control means havingan operation cycleto connect said periodic current sources to saidtransmitting circuit, office means connected to said transmittingcircuit energized to initiate an operation cycle of said control meansin response to an impulse of direct current created in the transmittingcircuit due to the closing of any one of the arming switches, and meansgovernedby each receiving device to connect the associated circuitextension to .a high voltage source of direct current to fi1'6 thedetonator of a mine whose arming switch is closed.

11. In combination, aplurality of mines each of which is provided withan arming switch and a detonator, a transmitting circuit between a dis-n-tribution poin'tarid a remote office, acircuit'extension for eacnv mineconnected to said transmitting circuit "at said point and including therespective detonatorand arming switch, an oflice source of directcurrentconnected to said transmitting circuit; a control relay connectedtothecircuit'at said point to been'ergized by said source of direct current,said control relay having a front contact interposed ineach of saidcircuit extensions, selective means'including'ofiice sources of periodiccurrents of differentxfrequenc'ies and receiving devices connectedacross 'said'transmitting circuitrat said distribution point there beinga preselected source and device assigned to each mine, each said deviceenergized only by current of the'frequency of the respective source andconnecting when energized-the associated circuit extension to thetransmitting circuit, office indication relays one for each mine,oflicecontrol means provided with'an operation cycle-having anindication portion and a firing portion, said control means connectingthe indication relay and periodic current sourceof the different minesto said circuit successively during said indication portion to energizethe indication relay of any mine whose arming switchiis.closed,'means'controlled by said indication relays and said controlmeans to connect the periodic current sources and a firing currentsource to said circuit during said firing portion to fire the detonatorof 7 any mine whose arming switch is closed, and oflice means connectedto said circuit energized to initiate'operation of said control means bythe current impulse created in said circuit when any arming switch isclosed. I p

e 12. In combination, a mine provided With'a normally open arming switchand a detonator which when supplied with current of a preselected highvoltage fires the mine, a transmitting circuit :between the mine and aremote office and normally excited with an ofiice source of directcurrent of a preselected low voltage, a control relay connected acrosssaid circuit normally energized by said-low voltage source, a lowresistance path including a front contact of said controlrelay and saidarming switch to shunt said circuit when the arming switch is closed, areceiving device connected to said circuit and excited only by currentof a preselected frequency, another circuit path including saiddetonator and said arming switch connected across said circuit when saidreceiving device is excited, an ofiice indication relay, an ofiicesource of current of said preselected frequency, an office source ofcurrent of said preselected high voltage, office control means set intooperation in response to the increase of current flowing in said circuitcaused by said low resistance path to connect said preselected frequencycurrent-source to said circuit and to interpose-said indication relay inthe connection of said low voltage current source to energize saidindication relay due to said other circuit path, and means controlled bysaid indication relay and said control-means to connect said preselectedfrequency current source and said high voltage current source to saidcircuit to fire the mine due to said other circuit path.

13. In combination; a mine provided with an arming switch, a detonatorand a resetrelay; -a transmitting circuit between said mine-and a re--mote 'ofiice' and normally excited by an ofiice energized by saidsource of low voltage direct current, afirst circuit path including afront contact of said control relay and said arming switch to shunt saidcircuit when the arming switch is closed, a receiving device connectedto said circuit and energized only by periodic current of a preselectedfrequency, a second circuit path completed by said device when energizedto connect said reset relay and said detonator to said circuit inmultiple; c-mce equipment including a source of periodic current of saidpreselected frequency, a source of direct current of said high voltage,a source of current of particular characteristic, an ofiice indicationrelay and a control means; means governed by said control means toconnect said indication relay and said periodic current source to saidcircuit to energize said indication relay by current supplied by saidlow voltage current source through said second circuit path, meansgoverned by said indication relay and said control means to connect saidperiodic current .source and said high voltage current source to saidcircuit to fire said detonator, other means governed by said controlmeans to connect said periodic current source and said source of currentof particular characteristic to said circuit to energize said resetrelay, and means connected to said circuit and energized by the impulseof current created in said circuit by said first circuit path to governsaid control means.

14. In combination, a transmitting circuit, a receiving device includinga filter and a gas triode tube, said filter tuned to pass only periodiccurrent of a preselected frequency and interposed between said circuitand a control electrode of said tube, said tube having its anode tocathode space interposed in a circuit extension connected across saidtransmitting circuit, a circuit path including an operating element anda normally open controller contact connected across said circuitextension, said operating element actuated only when supplied withdirect current of a preselected high voltage; a remote office providedwith an indication rela a source of periodic current of said preselectedfrequency, a direct current source of said preselected high voltage anda direct current source of a preselected low voltage; means tosimultaneously connect said periodic current source and said indicationrelay in series with said low voltage current source to said circuit toenergize said indication relay through said receiving device when saidcontroller contact is closed, and other means to simultaneously connectsaid periodic current source and said high voltage current source tosaid circuit to actuate said operating element through said receivingdevice when said controller contact is closed.

15. In combination, a transmitting circuit, a receiving device includinga filter and a gas triode tube, said filter tuned to pass only periodiccurrent of a preselected frequency and interposed between said circuitand a control electrode of said tube, said tube having its anode tocathode space interposed in a circuit extension connected across saidtransmitting circuit, a circuit path including an operating element anda normally open controller contact connected across said circuitextension, said operating element actuated only when supplied withdirect current of a preselected high voltage; another circuit pathineluding a filter and a reset relay connected across said circuitextension, said last mentioned filter tuned to pass only current of agiven low frequency and said reset relay operable when energized toactuate said controller contact; a remote ofiice provided with anindication relay, a source of periodic current of said preselectedfrequency, a source of direct current of said preselected high voltage,a source of direct current of a preselected low voltage and a source ofsaid low frequency current; means to simultaneously connect saidperiodic current source and said indication relay in series with saidlow voltage source to said circuit to energize said indication relaythrough said receiving device when said controller contact is closed,means to simultaneously connect said periodic current source and saidhigh voltage current source to said circuit to actuate said operatingelement when said controller contact is closed, and means tosimultaneously connect said periodic current source and said lowfrequency current source to said circuit to energize said reset relaythrough said receiving device.

16. In combination; a mine provided with an arming switch, a detonatorand a reset device; said detonator to fire the mine only when suppliedwith current of a preselected high voltage and said reset device toactuate the arming switch to disarm the mine only when supplied withcurrent of a given characteristic, a transmitting circuit, a receivingdevice including a filter and a gas triode tube connected to saidcircuit, said filter tuned to pass only periodic current of apreselected frequency, said tube having its anode to cathode spaceinterposed in a circuit extension connecting saidmine to said circuit; aremote oflice provided with an indication means, a source of periodiccurrent, a source of direct current of said preselected high voltage, asource of direct current of a preselected low voltage and a source ofcurrent of said given characteristic; and oilice control means operableto progressively and selectively connect said indication means and saidseveral current sources to said circuit as required to excite saidreceiving device for indicating the arming of the mine, for firing themine and for disarming the mine when not fired.

17. In combination; a mine provided with an arming switch, a detonatorand a reset device; said detonator to fire the mine only when suppliedwith current of a preselected high voltage and said reset device toactuate the arming switch to disarm the mine only when supplied withcurrent of a given characteristic, a transmittin circuit, a receivingdevice including a filter and a gas triode tube connected to saidcircuit, said filter tuned to pass only periodic current of apreselected frequency, said tube having its anode to cathode spaceinterposed in a circuit extension connecting said mine to said circuit;a remote office provided with an indication means, a source of periodiccurrent, a, source of direct current of said preselected high voltage, asource of direct current of a preselected low voltage and a source ofcurrent of said given characteristic; said low voltage current sourcenormally connected to said circuit; normally inactive oilice controlmeans operable to progressively and selectively connect said indicationmeans and said several current sources to said circuit as required toexcite said receiving device for indicating the arming of the mine, forfiring the mine and for disarming the mine; and means including atransformer interposed in said circuit at said ofiice and a controlrelay connected across the circuit at said mine and controlled by saidarming switch to create an electromotive force to initiate operation ofthe control means when said mine is armed.

ALFRED B. MILLER.

